Such electromagnetic actuators serve to operate valves, such as exhaust gas return valves to control the amount of exhaust gas returned to the combustion chamber, or secondary air valves to control the amount of secondary air introduced into the exhaust gas piping, which are used to reduce pollutants in internal combustion engines.
The actuator housing in these valves is usually axially fastened by screws to the flow housing via a flanged connection with a sealing being interposed. In the electromagnetic valves, a yoke plate frequently defines the axial termination of the actuator so that the actuator is delimited at its side facing the flow housing by the yoke plate in the interior of which the core of the electromagnetic circuit is arranged. The yoke plate accordingly serves as a flange of the actuator, while the actuator housing radially surrounding the electromagnet is injection-molded around the coil, wherein the yoke plate serves as an axial boundary surface during the injection molding process. The connection between the yoke plate and the actuator housing is established via the core which is pressed into the yoke plate. Establishing the flanged connection via the yoke plate has the advantage that the plastic body of the actuator does need not be screw-fitted so that a leak due to creep processes of the plastic material is to a large extent avoided.
Such a valve which serves as an electromagnetically operable secondary air valve is described, for example, in DE 10 2008 050 252 A1. This valve controls, via a globe valve, whose valve rod is connected with the armature of the electromagnet, an amount of air to be supplied to the exhaust gas pipe and pumped by a secondary air pump by adjusting, via operation of the electromagnet, a flow cross-section between a fluid inlet duct and a fluid outlet duct connected with the exhaust gas pipe. The valve comprises a non-return flap to prevent the air from flowing back when exhaust gas pulsations occur which is pressed against the valve seat when the valve is closed. In this valve, an O-ring acting as a sealing is pressed in between the yoke plate and the flow housing, which O-ring prevents liquid from entering between these component parts and possibly reaching and damaging the coil.
It has turned out, however, that a gap also exists between the yoke plate and the injection-molded actuator housing, which gap is large enough to allow spray water to enter the actuator from outside and to above all damage the electric component parts of the electromagnet.